Thursday, February 9, 2012

Superplastic Forming

Thermo forming process
Vacuum Forming

Vacuum forming is a superplastic forming process in which a gas pressure differential is imposed on the superplastic diaphragm, causing the material to form into the die configuration. Sometimes called stretch forming, the applied pressure is limited to atmospheric pressure (that is, 100 kPa, or 15 psi), and the forming rate and capability are therefore limited.

The rate of pressurization in blow forming is normally established such that the induced strain rates in the forming sheet are maintained in the superplastic range. The rate of pressurization is determined by trial and error, or by the application of analytical modeling methods. This pressure is generally applied slowly rather than abruptly to prevent too rapid a strain rate and consequent rupturing of the material. This information

With blow forming, additional pressure is applied from a gas pressure reservoir, and the only limitations are related to the pressure rating of the system and the pressure of the gas source. A maximum pressure of 690 to 3400 kPa (100 to 500 psi) is typically used in this process. The blow forming method is illustrated in the diagram, which shows a cross section of the dies and forming diaphragm. In this process, the dies and sheet
material are normally maintained at the forming temperature, and the gas pressure is imposed over the sheet, causing the sheet to form into the lower die; the gas within the lower die chamber is simply vented to the atmosphere. The lower die chamber can also be held under vacuum, or a
back pressure can be imposed to suppress cavitation if necessary.
TopOfBlogs RSS Search blogarama - the blog directory
Yellow Pages for USA and Canada blogville RSS Feed Directory